GB698406A - Improvements in or relating to magnetic escapement mechanism - Google Patents

Abstract

698,406. Timepieces. HORSTMANN CLIFFORD MAGNETICS, Ltd., and CLIFFORD, C. F. May 17, 1950 [May 28, 1949]. No. 14326/49. Class 139. A magnetic escapement in which relatively rotatable and oscillatable parts are coupled together magnetically so that the speed of rotation of the rotor is controlled by the frequency of oscillation is characterized by a rotor having at least one projection on its periphery and a cooperating stop member mounted to be just clear of the projection at normal escapement speed of the rotor, said rotor and said stop member being mounted for secondary vibration relative to each other, the natural frequency of said secondary vibration being so chosen as to be in excess of the natural frequency of oscillation of the escapement mechanism and impulsed, during rotation of the rotor at normal speed, in damped or out of tune frequency, and whereby the stop member is adapted to be contacted by the rotor projection by reason of the relative increase of amplitude of the secondary vibration only when the rotor rotates, on disruption of the normal magnetic coupling, at a speed sufficient to impulse the secondary vibration at or close to its natural frequency. The invention is applied to the type of magnetic escapements described in Specifications 596,216 and 660,581. The oscillator, Fig. 1, comprises a U-shaped magnet 2 carried by a plate spring 3 and the rotor is the escape wheel 1 mounted on a shaft 9. One end of a stop member 8 lies adjacent the peripheral extensions 7 of the rotor. As the rotor 1 rotates a transverse vibration is imparted thereto and if the rotor " runs away" from the oscillator the amplitude of this vibration will increase until the stop member 8 abuts an extension 7 to arrest the rotor. The transverse vibration of the rotor is produced by any static or dynamic out of balance of the rotor and shaft assembly and/or the impulses resulting from the reaction of. the poles of the magnet 2 on the escape wheel 1. In another example, Fig. 2, the stop member is a permanent magnet 12 impulsed to vibrate in a lateral direction by interacting magnetically with the rotor 1. When the rotor " runs away " from the oscillator 2 the amplitude of the vibration of the magnet 12 increases until it abuts an extension 7 and arrests the rotor 1.